GB1347864A - Method of producing a welded tube with a helical seam from a helically wound metal strip - Google Patents

Abstract

1347864 Welding by pressure and fusion MANNESMANN AG 19 April 1971 [13 Feb 1970] 20352/71 Heading B3R In producing a welded tube with a helical seam from a helically wound metal strip 2 wherein the edges of the strip are connected by pressure welding over only a part of the thickness of the strip and the joint is completed by fusion welding, a simply bevelled edge 16 of the strip is pressure welded to one surface 24 of the other, V bevelled, strip edge by high frequency current conducted to the strip edges by contacts 12, 14, the contact supplying the flat bevelled edge being further from the weld point 10 than the other contact and the simply bevelled edge and the one surface of the V bevelled edge being substantially parallel to each other and opposite each other in the zone where both edges are heated. In an embodiment in which the strip 2 is fed from above the tube axis the edge 16 is simply bevelled and the opposite edge is V bevelled and the edge 16 to be welded to the surface 24 of the V bevelled edge is preheated, by current from contact 12 engaging the outside of the tube, over the area 26 while the opposite edge is preheated over the area 28 by current from contact 14. A roller 11 may be arranged at the weld point 10 and the V remaining on the inside of the tube is filled by fusion welding. Alternatively the edge 16 may be V bevelled and the other edge simply bevelled, the contact 14 then being further from the weld point than the other contact and the fusion welding is effected from outside the tube. The strip may be fed from below the tube axis and in this case the contacts are arranged within the tube.